1. Field of the Invention
The present invention relates to secondary explosive aromatic nitro compounds and more particularly to polynitropolyphenyls having heat resistant properties. The improved thermal stability and high initiation sensitivity of the present invention make it particularly suitable for utilization in booster cups and exploding bridge wire (EBW) detonators. The present invention also relates to methods for preparing this compound.
2. Brief Description of the Prior Art
The practical use of secondary explosives requires two important properties: good thermal stability and high initiation sensitivity. The problem in developing secondary explosives has always been the negative correlation between these two properties. When a molecule is constructed in such a way that it is extremely stable in high temperature environments it often proves to be so stable that it resists valid detonation attempts.
In addition to the properties of thermal stability and initiation sensitivity, a secondary explosive must have adequate oxidative potential to result in a detonable material. In the case of polynitropolyphenyls, the compound must have a certain number of nitro groups to meet this threshold of detonability. The ideal compound is one that is thermally stable, has high explosive potential due to the large number of nitro groups in the molecule and has a high but controllable sensitivity to initiation.
Over the years several explosive polynitropolyphenyl compounds have been developed which exhibit in varying degrees the properties of good thermal stability and high initiation sensitivity. Among these are 2, 2', 4, 4', 6, 6'-hexanitrobiphenyl (HNB), 2, 2', 2", 4, 4', 4", 6, 6', 6"-nonanitroterphenyl (NONA) (U.S. Pat. No. 3,755,471 to Dacons), 2, 2", 4, 4', 4", 6, 6', 6"octanitro-m-terphenyl (ONT) (U.S. Pat. No. 3,592,860 to Dacons), and 2, 2', 2", 2'", 4, 4', 4", 4'", 6, 6', 6", 6'"-dodecanitorquaterphenyl (DODECA) (U.S. Pat. No. 3,450,778 to Dacons). The present invention, 1,3,5-trinitro-2,4,6-tripicrylbenzene (TNTPB) has a higher thermal stability than DODECA or NONA. ONT, which has a thermal stability slightly greater than the present invention, has a greatly reduced sensitivity to initiation and cannot be used in many situations. HNB has good thermal stability but it is a liquid at 260.degree.-300.degree. C. and is of little practical value as a high temperature explosive.
Among the many ways secondary explosives are used is as detonators used for oil well perforation. It is particularly important when perforating a well that the explosive used not decompose at high temperatures because of the high temperatures encountered in the drill hole. The explosive used, however, must also be sensitive enough that detonation can be easily initiated. The present invention fills the need both within the oil and gas industry as well as within other industries for a more thermally stable secondary explosive which can be readily detonated.